I have an interesting problem with our ASA 5510. We have a few Cisco 7960 VoIP phones which can make calls but are unable to receive calls after a few hours.
My thought was that the ASA was causing an issue with SYN/ACK messages coming from the phones and being denied due to no matching SYN and causing half open connections on the phones until the phone can no longer receive any new connections. I've seen this happen in the logs before.
this was "fixed" with:
service resetinbound interface outside
service resetinbound interface inside
However, I'm not seeing any denied SYN/ACK messages now and the phones are having this issue. The only way I know to temporarily resolve it is to re-enter the dynamic nat configuration, and then the phones begin to work again.
The phones are configured for SIP, and are using our ISPs IPBX to register.
I've attached the ASA config. If anyone has any input on this, it will be greatly appreciated.